Limited oxygen index LOI: under the stated experimental conditions, the material can be maintained the combustion state needed the oxygen minimum concentration of oxygen-nitrogen mixture gas.

Testing method: placed a certain size sample on the sample holder, adjusting the ratio of oxygen and nitrogen, igniting the sample with a specific igniter, makes the sample self-extinguishing after burning the certain time(2 minutes), or certain damage length (40mm), under this condition, according to the oxygen /nitrogen flow to calculated the LOI.